WASHINGTON » President Barack Obama said today that North Korea can no longer create an international crisis with nuclear provocations, asserting the United States and South Korea are fully capable of defending themselves.

“The days when North Korea could create a crisis and elicit concessions, those days are over,” Obama said from the White House East Room, after he and South Korean President Park Geun-hye met privately in the Oval Office.

Obama’s comments came in a news conference with Park on her first foreign visit as the country’s leader. It marked the 60th anniversary of the U.S.-South Korean alliance.

Obama said that Pyongyang has failed to drive a wedge between the U.S. and South Korea or to garner global respect with its threats. He says the joint U.S.-South Korea meeting at the White House was evidence that North Korea has “failed again.”

Ahead of the meeting, U.S. officials said North Korea has taken a step back from its recent escalation of regional tensions by removing from its launch site a set of medium-range ballistic missiles that had been readied for possible test-firing.

Obama says he doesn’t know North Korean leader Kim Jong Un personally and has never spoken to him, but says he can still take a different path. He said actions by the unpredictable young leader, who came to power after the death of his father Kim Jong Il in December 2011, seem to pursue a dead end.

“There’s going to have to be changes in behavior,” Obama said. “We have an expression in English, ‘Don’t worry about what I say, just watch what I do.'”

Park arrived at the White House with a color guard lining the driveway from Pennsylvania Avenue. Her Oval Office meeting, working lunch and joint news conference with Obama will be followed Wednesday by an address to a joint meeting of Congress.

Obama said such an address is an honor “reserved for our closest of friends.” He called Park “tough,” spoke of a great friendship between the two nations and joked that “the Korean wave” of culture has hit the United States.

“My daughters have taught me a pretty good ‘Gangnam Style,'” Obama joked, a reference to the hit dance song by South Korean singer PSY that has become YouTube’s most watched video with 1.5 billion views since its release last summer.

Park has had something of a baptism of fire since she took office in February, two weeks after North Korea’s latest atomic test ratcheted up tensions on the divided Korean Peninsula and undermined her hopes of forging a more trusting relationship with a difficult neighbor.

“Instead of just hoping to see North Korea change, the international community must consistently send the message with one voice, to tell them and communicate to them that they have no choice but to change,” Park said.

After the U.N. Security Council tightened sanctions on North Korea in response to the nuclear test — its third since 2006 — it claims to have scrapped the 1953 Korean War armistice and has threatened nuclear strikes on the U.S., prompting Washington to bolster missile defenses.

Two Musudan missiles at a site in eastern North Korea had been in what American officials described as launch-ready status for some weeks. Two U.S. officials confirmed their removal on condition of anonymity because they were not authorized to publicly discuss a matter involving sensitive U.S. intelligence. It’s not clear why they removed the missiles in recent days, but Pentagon press secretary George Little said on Monday that U.S. officials have seen a “provocation pause” by North Korea.

Park touched down in New York on Monday, meeting first with U.N. Secretary-General Ban Ki-moon, a former South Korean foreign minister who praised her “firm but measured” response to North Korean provocations and determination to resolve their differences though dialogue.

However, Park made clear in an interview on the eve of her visit that she was willing to get tough on North Korea. She told CBS News that if South Korea came under attack, “We will make them pay.”

Park, the first democratically elected female leader in Northeast Asia, is no stranger to Seoul’s Blue House, as the residence of the chief executive is known. She’s the daughter of the late South Korean dictator Park Chung-hee, and in her 20s she took over the duties of first lady for five years after a gunman claiming orders from North Korea killed her mother in a botched attack targeting her father.

While focused squarely on the North Korean threat, Park’s visit is a chance to build a rapport with Obama, who enjoyed an unusually close bond with the previous South Korean leader, Lee Myung-bak. The two presided over the adoption of a U.S.-South Korean free trade pact in 2012 that expanded the scope of an alliance largely built on security ties and deterring an attack from the North. Some 28,500 U.S. troops are still based in South Korea for that purpose.

Lee took a hard line on relations with Pyongyang, cutting aid to the impoverished nation. While his approach had Obama’s firm backing, public frustration in the South has mounted over the North’s continued weapons tests and provocations — including attacks in 2010 that left dozens of South Koreans dead.

In a change of tone, Park, although a conservative, has advocated trying to build trust with Pyongyang through aid shipments and large-scale economic initiatives if there’s progress on the nuclear issue, even as she and South Korea’s military promise to respond forcefully to any possible attack from the North.

But to date, relations have only gotten worse. Most recently, North Korea has withdrawn its 53,000 workers from an industrial park on its territory run by South Korean companies. After Pyongyang rejected Seoul’s offer of talks, the South last week withdrew its last staff from the facility, closing the last remaining symbol of inter-Korean cooperation that began during the “sunshine” engagement policy championed by Lee’s more liberal predecessors.

On Tuesday, North Korea threatened the U.S. and South Korea over joint naval drills taking place this week in the Yellow Sea. The section of the Korean People’s Army responsible for operations in North Korea’s southwest said it will strike back if any shells fall in its territory during the drills. Should the allies respond to that, the statement said, Pyongyang’s military would then strike five South Korean islands that stand along the aquatic frontline between the countries.

Daniel Russel, White House senior director for Asian affairs, said Obama would reaffirm the U.S. commitment to the defense of South Korea. He said the joint appearance of the two leaders at the White House would make it crystal clear to Pyongyang that the allies stand shoulder to shoulder.

“In dealing with North Korea, it’s vital we show unity,” Russel told reporters.

Dealing with Pyongyang’s secretive regime, never easy, has become increasingly tough under the unpredictable young leader Kim Jong Un, who came to power after the death of his father Kim Jong Il in December 2011.

Russel cautioned it was premature to judge whether North Korea’s cycle of provocation “is going up, down or zigzagging.” He said both the U.S. and South Korea support “incremental engagement” with Pyongyang, but it has to take “irreversible steps” signaling a commitment to end its nuclear program.

The past year has already seen disconcerting progress in the North’s weapons development, including its first successful launch of a three-stage, long-range rocket, although it is not yet believed to have to have the means to fire a nuclear-tipped missile at mainland America.

The Obama administration has put increasing emphasis on the role the North’s main ally and benefactor, China, can play to press Pyongyang to honor its previous commitments on denuclearization. In a significant move, one of China’s biggest banks said Tuesday it has halted business with a North Korean bank accused by the U.S. of financing Pyongyang’s missile and nuclear programs in the latest sign of Beijing’s displeasure with its estranged ally.

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Associated Press writers Robert Burns, Nedra Pickler and Jim Kuhnhenn contributed to this report.